One of the biggest impediments for achieving useful quantum computing is noise. The widely accepted solution to this challenge is fault-tolerant quantum circuits, however, it is out of reach for currently available processors to achieve computation at utility scale. Instead, we argue that quantum error mitigation enables access to accurate expectation values even on existing, noisy quantum computers. Establishing the applicability of these techniques at scales beyond those accessible to brute force classical methods is a crucial step toward probing a computational advantage with near-term noisy quantum computers. Here we experimentally demonstrate the efficacy of an error mitigation technique, zero-noise extrapolation, for quantum circuits using up to 127 qubits. The accuracy of the mitigated expectation values is greatly enhanced by novel advances in the coherence of large-scale superconducting quantum processors, and the ability to controllably scale noise at this scale. These experiments demonstrate an important tool for the realization of near-term quantum applications in a pre-fault tolerant era.

Youngseok Kim is Research Staff Member at IBM T.J. Watson Research Center. At IBM, he has been working toward calibrating device aiming to maintain the best performance for near-term intermediate scale quantum algorithm. His primary research interest is to explore opportunities in device level optimization domain for noisy intermediate scale quantum computer, pushing advances toward demonstrating useful quantum computing.

Youngseok Kim received B.S. degree in Electrical Engineering from POSTECH, South Korea, M.S. and Ph. D. degrees in Electrical and Computer Engineering from University of Illinois at Urbana and Champaign.